Duct access section

ABSTRACT

A combination duct access section which, installed in a duct, provides the duct with an access opening, a transparent inspection door, and/or a vacuum relief valve.

United States Patent [19] Turner 1 Jan. 1,1974

[ DUCT ACCESS SECTION [75] Inventor: Lloyd Bowman Turner, Columbus,

Ohio

[73] Assignee: United McGill Corporation,

Columbia, Ohio [22] Filed: June 30, 1972 [21] Appl. No.: 267,990

[52] US. Cl 137/467, 137/526, 137/559 [51] Int. Cl. F16k 17/04 [58]Field of Search 137/357, 358, 467,

[56] References Cited UNlTED STATES PATENTS 2,452,612 11/1948 Swenberg137/526 X 3,189,042 6/1965 Kerley et a1. 137/526 X 3,340,890 9/1967Raskhodoff 137/559 X 1,856,881 5/1932 Moss 220/24 H 2,506,737 5/1950Paquin 137/469 Primary ExaminerAlan Cohan Assistant Examiner-Gerald A.Michalsky Attorney-Wi1liam A. Strauch et a1.

[5 7 ABSTRACT A combination duct access section which, installed in aduct, provides the duct with an access opening, a transparent inspectiondoor, and/or a vacuum relief valve.

20 Claims, 5 Drawing F'gnres PATENTEU 1 I974 FIG I FIG. 4

DUCT ACCESS SECTION BACKGROUND OF THE INVENTION This invention relatesgenerally to an access section for an air duct, and more particularly toa novel access section which can be installed in a high velocity airduct immediately downstream of a fire damper which operates underpredetermined conditions to obstruct air flow through the duct.

In a high velocity air duct system, a fire damper of the type, forexample, shown in US. Pat. Nos. 3,467,163 and 3,485,284, is usuallyprovided for safety reasons in the air duct between the air blower andair outlets. The fire damper is maintained in a normal open position topermit air flow through the duct, but is closed to prevent passage offire as well as obstruct air flow when an excessively high temperaturecreates an emergency condition within the duct and area receiving theair.

Industry regulations require that a fire damper be inspected and testoperated at regular intervals to ensure that it will operate when neededin time of emergency. Thus, some arrangement must be provided forpermitting access to the damper for periodic inspection and- /ortesting, or for enabling resetting of the damper in case it should besomehow accidentally actuated to a closed position.

In such a high velocity air duct system employing a tire damper, as thefire damper is slammed shut, the inertia of the rapidly moving column ofair downstream of the damper develops a substantial vacuum in the ductimmediately downstream of the suddenly closed damper. That vacuum iscapable of collapsing and damaging the ductwork. When this occurs, aconsiderable amount of time and expense are required to repair theductwork and place the overall system back into operation.

With these requirements and problems in mind, development work wasinitiated to provide an arrangement which would not only satisfyindustry requirements for inspection and maintenance, but would alsoafford a solution to the problem of ductwork collapse upon rapid closureof the fire damper.

SUMMARY OF THE INVENTION Accordingly, the primary object of thisinvention resides in the provision of a novel duct access section whichaffords quick and easy accessibility into a duct, permits visualinspection of the interior of the duct, and/or provides vacuum relief ata safe negative pressure to prevent duct collapse.

Another object of this invention resides in the provision of a novelduct access section which provides a duct with an access opening, atransparent inspection door, and/or a vacuum relief valve.

Another object of the invention resides in the provision of a novel ductaccess section of simple construction which performs the three essentialfunctions of inspection, maintenance accessibility, and vacuum reliefprotection in a high velocity air duct system of the type describedabove.

Still another object of the invention resides in the provision of anovel, combination access section for use in a duct system immediatelydownstream a fire damper unit, with the access section providing readyaccess to and inspection of the fire damper and also providing a vacuumrelief valve for the duct to prevent its collapse upon rapid closure ofthe fire damper.

A further object of the invention resides in the provision of a novelaccess section for a duct, the section including a transparent cover ordoor mounted on the side wall of the duct by a plurality of releasable,spring lock members which enable the cover to be displaced inwardly intothe duct by hand to provide an access opening, or automatically inresponse to a predetermined, safe vacuum or negative pressure within theduct. The transparent, releasable door affords quick visual inspectionof the interior of the duct and/or fire damper located therein, providesa quick and easy access opening to the interior of the duct whennecessary, and acts as a vacuum relief valve to prevent the col lapse ofthe duct under emergency negative pressure conditions.

Other objects and advantages of the invention will become apparent fromreading the following detailed description of a preferred embodiment ofthe invention, wherein reference is made to the accompanying drawings inwhich like elements are indicated by like numerals.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a fragmentary, schematicillustration of a high velocity air duct system in which the novelaccess section of the invention is particularly useful;

FIG. 2 is a perspective view of a novel duct access section constructedaccording to the invention;

FIG. 3 is a fragmentary sectional view taken generally along lines 3-3of FIG. 2, illustrating in particular the manner in which the releasablelock members mount the transparent door on the door frame;

FIG. 3A is a fragmentary sectional view similar to FIG. 3 illustratingan insulated access door provided for gas flow systems and fluid ductswhich are required to be insulated.

FIG. 4 is a fragmentary front view illustrating the re leasable lockmembers.

DETAILED DESCRIPTION OF THE INVENTION As shown in FIG. 1 of thedrawings, a high velocity air duct system 10 includes a fan or blower 12which delivers pressurized air to a sheet metal distributing duct 14having branched outlets 16 which lead into a room or other area 18 towhich air is to be supplied. A fire damper unit 20 is connected betweenfan 12 and duct 14 and is usually in an open position to permit air flowthrough duct 14. Under emergency conditions, the damper 20 is actuatedto a closed position to obstruct air flow between the fan 12 and duct 14and to prevent passage of fire past the damper.

As discussed above, area 22 of duct 14 immediately downstream of firedamper unit 20 is subject to inward collapse following rapid closure ofthe fire damper. This results from the creation of a hegative pressurein area 22 by the inertia of the column of air which is moving rapidlythrough duct 14. In accordance with this invention, a novel, combinationduct access and vacuum relief section 24 is inserted in duct system 10between the downstream end of fire damper unit 20 and duct 14.

Referring now to FIGS. 2-4, access section 24 includes a tubular, sheetmetal fitting 26, one end 28 to be connected to a duct downstream of, ordirectly to the downstream end of, fire damper unit 20 and another end30 to be connected to duct 14. A sheet metal, door housing 32, having agenerally rectangular cross section, is fastened as by welding, about anopening 34 in the side wall of fitting 26. Housing 32 may, for example,be formed by upper and lower wall plates 36 and 38 of about 12 inches ormore long and side wall plates 40 and 42 of about 8 inches or more long.The inner edges of plates 36, 38, 40, and 42, conform to the shape ofthe wall of fitting 26 so that all of the plates may be welded againstfitting 26. The outer ends of the plates are bent inwardly to provide asmall, rectangular door frame 43 which surrounds a rectangular accessopening 44 into housing 32 and fitting 26.

A transparent, shatterproof door 46, made from a plastic or similarmaterial, is releasably mounted inside of the frame 43 against a sealinggasket 47 which is made of rubber or the like and extends completelyaround the inside surface of frame 43. The mounting structure includes aplurality of releasable spring lock members 48. Door 46, also serving asa visual inspection port, is sized somewhat smaller than the rectangularcross sectional area of housing 32 so that the door may be displacedinwardly through the housing into the fluid passageway of fitting 26.

As shown in FIGS. 3 and 4, each of the releasable spring lock members 48is of a commercially available type and includes a body portion 50having a center section 52 which is fastened against the outer surfaceof door 46 by way of a pop rivet assembly 54. The body portion 50 alsoincludes a pair of spring arms 56, the free ends of which are formed asarcuate pivoting bearing surfaces 58. A locking lever or finger 60includes a pair of laterally extending pivot arms 62 of rectangularcross section mounted within bearing sections 58 of spring arms 56, withthe free end 63 of finger 60 adapted to engage the outer surface offrame 43 in the locked position of the lock member 48 as shown in fullline in FIG. 3. 7

With the lock members 48 positioned as shown in FIG. 3, door 46 islocked in place inside housing 32 against gasket 47 by the spring forceof spring arms 56. It is maintained in this locked closed position toblock access opening 44 until a sufficient inward force is appliedagainst the door to overcome arms 56 and move fingers 60 to the unlockeddotted line position of FIG. 3.

To facilitate manual displacement of door 46 inwardly through housing 32into fitting 26, a handle 66 is fastened to door 46. A flexibleretaining chain 68 has one end connected to handle 66 and its other endwelded at 70 to door frame 43 to retain door 46 within the accesssection after it has been opened.

It is apparent that the duct access section 24 provides the objects andadvantages which were set forth and discussed initially hereinabove. Forexample, with the transparent door 46 retained in place as shown in FIG.2, a visual inspection through door 46 of the fire damper unit in thesystem shown in FIG. 1 is readily feasible without necessitating theremoval or disturbance of any parts or shut down and interruption of thesystem. When it becomes necessary to physically inspect, test-operate,or reset fire damper unit 20, maintenance personnel need only to pushinwardly on handle 66 to release lock fingers 60 to the dotted lineposition shown in FIG. 3, and thereafter displace the entire door 46into the main flow passageway of fitting 26. Access to the fire damperunit 20 is thereby provided through the access openings 44, 42 and 34,and, when the required maintenance or inspection is completed,

door 46 is quickly and easily returned to its closed position simply byrelocking fingers against the outside surface of door frame 43.

During operation of air flow system I0, access system 24 preventscollapse of and damage to duct area 22 immediately following rapidclosure of the fire damper unit 20. As discussed previously, when thefire damper unit 20 rapidly closes it can block the air flow from fan 12and the inertia of the rapidly moving column of air in duct 14 causes avacuum or negative pressure to be developed in section 22 of the ductsystem. This negative pressure will act against the inside surface ofdoor 46 and, when it is sufficiently high to overcome the spring forceof arms 56, fingers 60 will be unlocked automatically and door 46 willbe pulled inwardly into fitting 26, thereby providing a vacuum reliefpassage through access openings 44, 42 and 34. In this way, door 46 andlock members 48 can be designed to open at a safe negative pressure andthe door will act as a vacuum relief valve for the overall duct systemto effectively prevent collapse of and damage to the ductwork.

The safe negative pressure required to overcome the spring force of arms56 to release door 46 may vary with various sized ductwork, but, ofcourse, in all cases it will be less than that at which collapse of theductwork will occur. For example, the negative pressure at which door 46will open may lie within a range of 3% inches to 7 /2 inches watercolumn. After door 46 has been opened and operated as a relief valve,tether chain 68 retains the door in the area of fitting 26 and preventsit from moving downstream into duct 14.

It will be apparent that during normal operation of system 10 thepressurized air flowing through fitting 26 forces door 46 outwardlyagainst gasket 47 to provide a tight pressure seal around the door frameopening 44 and prevent any leakage of air through opening 44.

Various modifications of access section 24 may be made without departingfrom the scope of the invention. For example, door 46 may be constructedof solid sheet metal, or it may be an insulated door consisting of adouble wall of sheet metal 64 with an intermediate layer ofinsulation65. In addition, the entire access section 24 may be fully insulated andincorporated in acoustical ductwork.

Although the access section 24 has been described for particular use incombination with a fire damper, it is, of course, not limited to such ause and may be employed in any ductwork to provide ready access intoand/or vacuum relief for the ductwork.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

l. A gas flow system comprising: a pressurized gas source; gas outletmeans; duct means for conveying gas from said source to said outletmeans; damper means mounted in said duct means for movement between anormally open position in which it permits gas flow through said ductmeans and a closed position in which it obstructs flow through said ductmeans; and means providing access to said damper means through anopening in the wall of said duct means downstream of said damper meansand including a closure member sealingly fitted to said wall opening andmounted on said duct means by resettable latch means normally biasingsaid closure member to seal said wall opening and actuated in responseto a negative pressure in said duct means to release said closure memberfrom its mounting on said duct means and provide vacuum relief for saidduct means.

2. The gas flow system of claim 1 wherein said closure member comprisesa transparent, shatterproof door serving also to provide a visualinspection port for viewing said damper means.

3. The gas flow system of claim 1 wherein said resettable latch meanscomprises spring biased pressure releasable latch means operative torelease said closure member from said duct means in response to aneffective inward pressure on said closure member.

4. The gas flow system defined in claim 3, said access means comprisinga tether chain connecting said closure member to said duct meansadjacent said opening.

5. The gas flow system defined in claim 1, said closure membercomprising a door comprising spaced metal walls and a layer ofinsulation therebetween.

6. The gas flow system of claim 1, wherein a tether chain is providedhaving one end connected to said closure member and its other endconnected to said duct means to retain the released closure memberwithin the access section of said duct means upon its release inresponse to releasing pressure.

7. The gas flow system defined in claim 1, wherein said access meanscomprises a tubular housing fixed to the wall of said duct meansdefining said opening and projecting laterally therefrom, the outer endof said housing having an inwardly directed framing fixed theretodefining an opening communicating with said opening in the wall of saidduct means, and sealing means mounted on said framing inside saidhousing, said closure member being mounted within said housing againstsaid sealing means to normally close said housing opening, but beingdisplaceable inwardly through said housing to provide access into andvacuum relief for said duct means.

8. A gas flow system comprising: a pressurized gas source, gas outletmeans, duct means for conveying gas from said source to said outletmeans, damp'er means mounted in said duct means for movement between anormally open position in which it permits gas flow through said ductmeans and a closed position in which it obstructs flow through said ductmeans, vacuum relief means mounted on said duct means downstream of saiddamper means, said vacuum relief means including a housing opening intosaid duct means and a closure member releasably'mounted in said housingby resettable latch means normally biasing said closure memher to sealsaid housing opening and actuated in response to a negative pressure insaid duct means upon closure of said damper means to release said latchmeans and said closure member from said duct means and provide vacuumrelief for said duct means.

9. A fluid duct comprising tubular wall means defining a fluidpassageway and access means in said tubular wall means including atransparent access door providing visual inspection of said fluidpassageway and removably mounted on said tubular wall means byresettable spring lock members normally biasing said access door to sealsaid access means and operable to release said access door to permitaccess to said passageway upon application of effective inward pressureto said door.

10. A fluid duct as defined in claim 9, comprising handle means on saidaccess door for manually releasing and remounting said access door.

11. A fluid duct comprising wall means defining a fluid passageway andan opening in said wall means, an access door for closing said opening,and mounting means for said access door comprising resettable springlock members mounting said access door on said duct means in position toclose said opening, said resettable spring lock members normally biasingsaid access door to seal said opening and being actuatable in responseto a negative pressure in said fluid passageway to free said access doorfrom its mounting on said duct wall means thereby providing a vacuumrelief for said passageway and access to said passageway.

12. A fluid duct as defined in claim 11, wherein said mounting meanscomprises a tubular housing fixed to said wall means in surroundingrelation to said wall opening and formed at its outer end to provide aninwardly directed door frame defining a door opening in communicationwith said wall opening and said resettable spring lock members mountsaid access door on said door frame.

13. A fluid duct as defined in claim 11, comprising a tether chainhaving one end connected to said access door and its other end connectedto said duct means to retain the freed door adjacent said wall opening.

14. A fluid duct as defined in claim 11, said access door beingconstructed of a transparent, shatterproof material providing for visualpassageway inspection.

15. A fluid duct as defined in claim 11, said access door being formedby spaced metal walls and a layer of insulation therebetween.

16. A fluid duct access section comprising a tubular wall defining afluid passageway, an opening in said wall, a tubular housing fixed tosaid wall around said opening and extending laterally therefrom, theouter end of said housing having an inwardly directed door frame fixedthereto and defining a door opening communicating with said wallopening, sealing means mounted on said door frame inside said housing,an access door, mounting means for releasably mounting said access dooron said door frame within said housing in sealing engagement with saidsealing means, said mounting means comprising resettable latch meansnormally biasing said access door against said sealing means andactuated in response to a negative pressure in said fluid passageway torelease said door from said door frame for movement inwardly throughsaid housing, thereby providing vacuum relief for said passagewaythrough said door opening.

17. A fluid duct access section as defined in claim 16, wherein saidaccess door is constructed of a transparent, shatterproof materialproviding for visual passageway inspection.

18. A fluid duct access section as defined in claim 16, wherein saidaccess door is formed by spaced metal walls with a layer of insulationtherebetween.

19. A fluid duct access section as defined in claim 16, said mountingmeans comprising pressure releasable spring lock means.

20. A fluid duct access section as defined in claim 16, comprisinghandle means connected to said access door and a tether chain to retainsaid access door in said access section.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,782,411 Dated January 1, 1974 Inventor(s) L'loyd Bowman Turner It iseertifi ed that error appears in the above-identified patent and thatsaid Letters Patent: are hereby corrected as shown below:

.Change Assignee's address from "Columbia" to Columbi1s-.

Signed. 'and sealed. this 7th de 0f May 197M...

(SEAL) Atte et:

EDWARD i LFLm cmmJR. 7 C, mRsHALL. DANN Attesting Officer Commissionerof Patents

1. A gas flow system comprising: a pressurized gas source; gas outletmeans; duct means for conveying gas from said source to said outletmeans; damper means mounted in said duct means for movement between anormally open position in which it permits gas flow through said ductmeans and a closed position in which it obstructs flow through said ductmeans; and means providing access to said damper means through anopening in the wall of said duct means downstream of said damper meansand including a closure member sealingly fitted to said wall opening andmounted on said duct means by resettable latch means normally biasingsaid closure member to seal said wall opening and actuated in responseto a negative pressure in said duct means to release said closure memberfrom its mounting on said duct means and provide vacuum relief for saidduct means.
 2. The gas flow system of claim 1 wherein said closuremember comprises a transparent, shatterproof door serving also toprovide a visual inspection port for viewing said damper means.
 3. Thegas flow system of claim 1 wherein said resettable latch means comprisesspring biased pressure releasable latch means operative to release saidclosure member from said duct means in response to an effective inwardpressure on said closure member.
 4. The gas flow system defined in claim3, said access means comprising a tether chain connecting said closuremember to said duct means adjacent said opening.
 5. The gas flow systemdefined in claim 1, said closure member comprising a door comprisingspaced metal walls and a layer of insulation therebetween.
 6. The gasflow system of claim 1, wherein a tether chain is provided having oneend connected to said closure member and its other end connected to saidduct means to retain the released closure member within the accesssection of said duct means upon its release in response to releasingpressure.
 7. The gas flow system defined in claim 1, wherein said accessmeans comprises a tubular housing fixed to the wall of said duct meansdefining said opening and projecting laterally therefrom, the outer endof said housing having an inwardly directed framing fixed theretodefining an opening communicating with said opening in the wall of saidduct means, and sealing means mounted on said framing inside saidhousing, said closure member being mounted within said housing againstsaid sealing means to normally close said housing opening, but beingdisplaceable inwardly through said housing to provide access into andvacuum relief for said duct means.
 8. A gas flow system comprising: apressurized gas source, gas outlet means, duct means for conveying gasfrom said source to said outlet means, damper means mounted in said ductmeans for movement between a normally open position in which it permitsgas flow through said duct means and a closed position in which itobstructs flow through said duct means, vacuum relief means mounted onsaid duct means downstream of said damper means, said vacuum reliefmeans including a housing opening into said duct means and a closuremember releasably mounted in said housing by resettable latch meansnormally biasing said closure member to seal said housing opening andactuated in response to a negative pressure in said duct means uponclosure of said damper means to release said latch means and saidclosure member from said duct means and provide vacuum relief for saidduct means.
 9. A fluid duct comprising tubular wall means defining afluid passageway and access means in said tubular wall means including atransparent access door providing visual inspection of said fluidpassageway and removably mounted on said tubular wall means byresettable spring lock members normally biasing said access door to sealsaid access means and operable to release said access door to permitaccess to said passageway upon application of effective inward pressureto said door.
 10. A fluid duct as defined in claim 9, comprising handlemeans on said access door for manually releasing and remounting saidaccess door.
 11. A fluid duct comprising wall means defining a fluidpassageway and an opening in said wall means, an access door for closingsaid opening, and mounting means for said access door comprisingresettable spring lock members mounting said access door on said ductmeans in position to close said opening, said resettable spring lockmembers normally biasing said access door to seal said opening and beingactuatable in response to a negative pressure in said fluid passagewayto free said access door from its mounting on said duct wall meansthereby providing a vacuum relief for said passageway and access to saidpassageway.
 12. A fluid duct as defined in claim 11, wherein saidmounting means comprises a tubular housing fixed to said wall means insurrounding relation to said wall opening and formed at its outer end toprovide an inwardly directed door frame defining a door opening incommunication with said wall opening and said resettable spring lockmembers mount said access door on said door frame.
 13. A fluid duct asdefined in claim 11, comprising a tether chain having one end connectedto said access door and its other end connected to said duct means toretain the freed door adjacent said wall opening.
 14. A fluid duct asdefined in claim 11, said access door being constructed of atransparent, shatterproof material providing for visual passagewayinspection.
 15. A fluid duct as defined in claim 11, said access doorbeing formed by spaced metal walls and a layer of insulationtherebetween.
 16. A fluid duct access section comprising a tubular walldefining a fluid passageway, an opening in said wall, a tubular housingfixed to said wall around said opening and extending laterallytherefrom, the outer end of said housing having an inwardly directeddoor frame fixed thereto and defining a door opening communicating withsaid wall opening, sealing means mounted on said door frame inside saidhousing, an access door, mounting means for releasably mounting saidaccess door on said door frame within said housing in Sealing engagementwith said sealing means, said mounting means comprising resettable latchmeans normally biasing said access door against said sealing means andactuated in response to a negative pressure in said fluid passageway torelease said door from said door frame for movement inwardly throughsaid housing, thereby providing vacuum relief for said passagewaythrough said door opening.
 17. A fluid duct access section as defined inclaim 16, wherein said access door is constructed of a transparent,shatterproof material providing for visual passageway inspection.
 18. Afluid duct access section as defined in claim 16, wherein said accessdoor is formed by spaced metal walls with a layer of insulationtherebetween.
 19. A fluid duct access section as defined in claim 16,said mounting means comprising pressure releasable spring lock means.20. A fluid duct access section as defined in claim 16, comprisinghandle means connected to said access door and a tether chain to retainsaid access door in said access section.